Well I respectfully disagree. I don't think it's too hard to figure out if someone is really a friend or just someone you've met a few times. And if add them just to "see what they're up to" then sure, you're going to get noise.
I also think if you're adding people to your Facebook that have anything to do with your employment you're insane.
But maybe it is because I am 30+ that these distinctions to me seem very clear.